From the corresponding Slack thread started by @Hghani:

There appears to be an anomalous trend in the per domain unique devices counts around May-June 2023 where we see an almost +100 million unique device count from May to June (North America only) in Wikipedia. The increase is exclusive to the mobile domains. This spreadsheet shows the increase in unique devices per domain is across-the-board larger than any other change in the month by a large margin. The numbers are fairly large and unprecedented in the last few years, but no corresponding effect is seen in per project family data. Since webrequest data doesn't go back that far it becomes hard to compare webrequest data like redirects to today (and the effect seems to have tapered off in the current months anyway). So I was curious if anyone had ideas or additional context/info about issues or changes that occurred in this timeframe? A simple visualization is attached.